I believe that this is not a valid answer because according to the Esolangs Wiki, all characters other than
<>,.+- are comments and are ignored. There is no extension listed on the wiki that behaves the way the user claims.
If there exists a language (SMBF as Zwei mentioned) or an interpreter that does behave that way, then it is a valid answer, but it is not a valid Brainf**k program as the user claims it to be.
For now, it is an invalid answer. If the user can provide an interpreter that behaves this way for either a BF variant or another similar language, then it is valid; however, if the user fails to provide a working interpreter (that was created before the challenge), then the answer is invalid and should be removed.
If a valid interpreter is created after a challenge, as @Riker said, it is still allowed as a non-competing answer, and shouldn't be deleted. If an interpreter was created specifically to address this challenge in zero or one byte(s), then it is usually not welcomed.
In this case, because the Hello World challenge is catalogue challenge, there are no "non-competing" answers, so even if the intepreter were created after the challenge, it would still be perfectly fine.
The answer doesn't even work.
The answer, when modified to actually work, would just be practically a duplicate of @mbomb007's answer.
The answer has since been deleted.